U.S. patent number 5,844,781 [Application Number 08/715,317] was granted by the patent office on 1998-12-01 for electrical device such as a network protector relay with printed circuit board seal.
This patent grant is currently assigned to Eaton Corporation. Invention is credited to James Leo Lagree, John Carl Schlotterer.
United States Patent |
5,844,781 |
Schlotterer , et
al. |
December 1, 1998 |
Electrical device such as a network protector relay with printed
circuit board seal
Abstract
An electrical device such as a network protector relay is
protected from ambient conditions by a housing having a printed
circuit board (PCB) providing a seal for the housing and air and
water tight connections between relay leads and external leads. The
relay leads are soldered in first plated through apertures in the
PCB substrate while the external leads are soldered in second
plated through apertures connected to corresponding first apertures
by conductive traces on the substrate. Potting material confined by
a potting dam electrically insulates the solder connections on the
external side of the PCB. Components can be mounted on either side
of the substrate by soldering the component pins or leads in
additinal plated through apertures electrically connected to relay
and/or external leads by the conductive traces. Components such as
connectors or indicators, including, for example, light emitting
diodes, can be supported in the potting dam and connected to
appropriate ones of the external leads insulated by the potting
material.
Inventors: |
Schlotterer; John Carl
(Franklin, PA), Lagree; James Leo (McKees Rocks, PA) |
Assignee: |
Eaton Corporation (Cleveland,
OH)
|
Family
ID: |
24873548 |
Appl.
No.: |
08/715,317 |
Filed: |
September 16, 1996 |
Current U.S.
Class: |
361/752; 361/796;
361/772; 174/50.5; 361/803; 361/736; 174/539 |
Current CPC
Class: |
H05K
5/062 (20130101) |
Current International
Class: |
H05K
5/06 (20060101); H05K 005/00 () |
Field of
Search: |
;361/819,752,796,803,736,679,772-774,777-779,760
;174/17CT,50.54,50.53,50.52,50.51,50.5,255,52.1,52.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Picard; Leo P.
Assistant Examiner: Vu; Phuong T.
Attorney, Agent or Firm: Moran; Martin J.
Claims
What is claimed is:
1. A network protector unit comprising:
a housing having an opening;
a relay mounted inside said housing and having relay leads
extending therefrom;
external leads outside said housing;
a printed circuit board having air tight and water tight electrical
connections connecting said relay leads to said external leads;
means securing said printed circuit board across said opening to
form an air tight and water tight seal for said housing;
wherein said printed circuit board comprises an insulative
substrate, and said air tight and water tight electrical
connections comprise plated through apertures extending through
said substrate and in which said relay leads are inserted from
inside said housing and said external leads are inserted from said
outside said housing and in which said relay leads and external
leads are secured by solder;
wherein said apertures include first plated through apertures in
which said relay leads are inserted from inside said housing and
secured with solder and second plated through apertures in which
said external leads are inserted from outside said housing and
secured with solder, and wherein said air tight and water tight
connections further include associated conductive traces on said
substrate electrically connecting corresponding ones of said first
and second plated through apertures;
wherein said printed circuit board has potting material applied
over at least some connections on an outer side of said substrate
external to said housing; and
wherein said printed circuit board has a potting dam confining said
potting material applied to said external said of said
substrate.
2. The network protecter relay unit of claim 1 including components
supported in said potting dam, connected to said external leads and
wherein said potting material electrically insulates said external
leads connected to said components.
3. Apparatus protecting from ambient conditions an electrical
device having device leads connecting to external leads, said
apparatus comprising:
a housing having an opening and in which said electrical device is
mounted;
a printed circuit board having a substrate and electrical
connections connecting said device leads to corresponding ones of
said external leads, said electrical connections including
apertures extending through said substrate in which said device
leads are inserted from inside said housing and said external leads
are inserted from outside said housing and in which said device
leads and external leads are secured by solder;
means securing said printed circuit board over said opening to form
an air tight and water tight seal for said housing;
wherein said apertures in said substrate comprise first plated
through apertures in which the device leads are secured by said
solder and second plated through apertures in which said external
leads are secured by said solder, and conductive traces on said
substrate electrically connecting said first apertures with said
second apertures for corresponding device leads and external leads;
and
dam means confining said electrically insulative material on said
side of said printed circuit boards.
4. Apparatus protecting from ambient conditions an electrical
device having device leads connecting to external leads, said
apparatus comprising:
a housing having an opening and in which said electrical device is
mounted;
a printed circuit board having a substrate and electrical
connections connecting said device leads to corresponding ones of
said external leads, said electrical connections including
apertures extending through said substrate in which said device
leads are inserted from inside said housing and said external leads
are inserted from outside said housing and in which said device
leads and external leads are secured by solder;
means securing said printed circuit board over said opening to form
an air tight and water tight seal for said housing;
wherein said means securing said printed circuit board across said
opening includes a sealing gasket and fastening means clamping said
sealing gasket between said printed circuit board and said housing
around said opening;
wherein said printed circuit board further has electrically
insulative material applied over said solder on an external side of
said printed circuit board; and
components supported by said dam means and connected to said
external leads which are electrically insulated by said
electrically insulative materials .
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electrical devices which are protected
from ambient conditions by sealing them in an air and water tight
housing through which electrical leads for the device must extend.
It has particular application to protective relays for network
protectors and uses a printed circuit board, through which the
external electrical connections to the device are made, as a cover
for the housing.
2. Background Information
In many installations, it is necessary to protect an electrical
device from environmental conditions while providing the device
with external connections to other apparatus. One such installation
is the relay for a network protector. The network protector is
apparatus used to control the flow of electrical power to a
distribution network such as a section of a city, a large building,
or an industrial site. Such a network is fed at multiple points
through transformers. The network protector includes a circuit
breaker and a relay which opens the circuit to the transformer upon
detection of abnormal current flow.
Typically, the transformer is mounted in a vault, frequently
underground. As the vault can contain water and the transformer can
over heat and even catch on fire, the circuit breaker and its
protective relay are mounted in a sealed tank. However, to further
protect the relay, it is mounted inside a sealed housing within the
tank. The protective relay requires numerous electrical connections
such as to current transformers which sense the network currents
and to the circuit breaker. Feed throughs in which the insulated
wires from the relay are clamped by a rubber gasket at the
penetration through the housing have not proved satisfactory, even
if the gasket is sealed tightly around the leads, as air and
moisture can leak between the conductor and the insulation and
along the individual strands of stranded leads. Now, the practice
is to use feed throughs in which glass plugs fuse short sections of
wire in apertures in a metal plate. The relay wires are soldered to
loops on the inner ends of the feed throughs, while corresponding
external leads are soldered to loops on the outer ends. Such feed
throughs are expensive.
There is a need therefore for improved arrangements for making
electrical connections to electrical devices enclosed in a housing,
and in particular to network protector relays.
There is a need for providing such improved arrangements which are
economical and practical to implement.
There is a further need for such arrangements which are air tight
and water tight.
SUMMARY OF THE INVENTION
These needs and others are satisfied by the invention which is
directed to apparatus for protecting electrical devices from
ambient conditions while providing electrical connections to the
device. The apparatus includes a housing having an opening and in
which the electrical device is mounted. A printed circuit board
comprising an insulating substrate and electrical connections for
connecting device leads to corresponding ones of external leads.
The electrical connections include plated through apertures
extending through the substrate in which the device leads are
inserted from inside the housing and the external leads are
inserted from outside the housing. The leads are secured in the
plated through apertures by solder. The apparatus further printed
circuit board over the opening in the housing to form an air tight
and water tight seal.
Preferably, the apertures in the substrate include first apertures
in which the device leads are secured by solder and second
apertures in which the external leads are secured by solder.
Conductive traces on the substrate electrically connect the first
and second apertures for corresponding device leads and external
leads.
Preferably, the printed circuit board has an electrically
insulative material applied over at least the solder connections on
the external side of the printed circuit board. Most preferably,
the insulative material is a potting material which is contained
within potting dams surrounding the portions of the printed circuit
board which are to be potted.
As another aspect of the invention, components can be mounted on
either side of the printed circuit board. In addition, components
such as connectors for the external wiring and indicators such as,
for instance, light emitting diodes (LEDs) can be supported in the
potting dam.
The invention has particular application to network protector
relays. The components mounted on the printed circuit board forming
the seal for the housing can include, for instance, auxiliary
current transformers, and burden resistors which convert the sensed
currents into voltages for input to the relay. These components can
be on either side of the printed circuit board, but preferably the
burden resistors are on the inside and the auxiliary current
transformers are on the outside.
BRIEF DESCRIPTION OF THE DRAWINGS
A full understanding of the invention can be gained from the
following description of the preferred embodiments when read in
conjunction with the accompanying drawings in which:
FIG. 1 is a schematic view of a network transformer having a
network protector including a network protector relay incorporating
the invention.
FIG. 2 is a longitudinal section through a network protector relay
and its housing in accordance with the invention.
FIG. 3 is an isometric view of a printed circuit board which forms
part of the relay enclosure shown with parts cut away.
FIGS. 4A-4C are fragmentary cross sectional views through portions
of the print circuit board showing lead connections in accordance
with three embodiments of the invention.
FIGS. 5A-5C are plan views of the connections of FIGS. 4A-4C.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The invention will be described as applied to the protection of a
network protector relay to which it has particular application. It
will be realized, however, that the invention has further
application to the protection of other types of electrical devices
from ambient conditions while providing connections between the
device and external wiring which are both air tight and water
tight.
FIG. 1 illustrates a network protector 1 used in conjunction with a
transformer 3 feeding a network 5, which for instance could service
a section of a city, a large building, an industrial site or other
local electrical distribution systems. The network 5 is fed by a
number of other transformers (not shown) similar to the transformer
3. Often, the transformer 3 with its network protector 1 is
installed in an underground vault 7 in which water can accumulate.
Thus, the network protector 1 is housed in a water and air tight
tank 9.
The network protector 1 includes a circuit breaker 11 and a relay
unit 13. A major function of the relay unit 13 is to detect
abnormal current flow through the transformer which could include
flow of current out of the network 5 through the transformer 3 in
the event of certain fault conditions.
The relay unit 13 includes a protective relay 15 and an enclosure
17 for the relay as seen in FIG. 2. The enclosure 17 includes a
housing 19 having an opening 21 at one end, which, as will be seen,
is closed by a closure in the form of a printed circuit board (PCB)
23.
The protective relay 15 in the preferred embodiment, is a digital
relay which, for example, includes a power PCB 25 and a processor
PCB 27 which are supported in spaced relation at one end by a
mounting spacer 29 secured to the PCB 23 which serves as a mother
board, and at the other end by a notched locator bracket 31 secured
to the housing 19. Electrical connections between the power PCB 25
and the processor PCB 27 are made by inter-board connectors 33. A
spacer 35 maintains a fixed spacing between the boards at the ends
supported by the PCB locator 31.
The printed circuit board 23 serves as a cover for the opening 21
in the housing. The board 23 is secured over the opening 21 by
screws 37 extending through the PCB 23 and sealed with O rings 39.
The screws 37 thread into mounting bosses 41 brazed to the inside
of the housing 19. A gasket 43 is clamped between the printed
circuit board 23 and the housing 19 to provide a water and air
tight seal.
The printed circuit board 23 also provides connections 45 between
relay leads 47 and external leads 49.
As seen more clearly in FIGS. 3 and 4A-C and 5A-C, the electrical
connections 45 include plated through apertures 51 in the printed
circuit board 23. In the preferred form of the invention, stripped
ends 47w of the relay leads 47 are inserted into first apertures
51a from the inner side 23a of the printed circuit board and
secured in place by solder 53. Similarly, the stripped end 49w of
the corresponding external lead 49 is inserted from the outer side
23b of the printed circuit board into a corresponding second plated
through aperture 57b spaced laterally from the aperture 51a and is
also filled with solder 53. The solder 53 is introduced into the
apertures 5a from the outer side 23b of the printed circuit board
23, while additional solder 53 is introduced into the apertures 51b
from the inner side 23a of the printed circuit board where there is
no interference from the lead being connected. In this manner, a
sound solder connection which is air tight and water tight can be
easily made. The corresponding solder filled apertures 51a and 51b
are electrically connected by an associated electrically conductive
trace 55 on the PCB 23. Such connected traces can be made on either
or both sides of the printed circuit board 23.
Even where the conductive traces 55 are on the inner side 23a of
the printed circuit board 23, there are exposed electrical
connections on the outer side 23b. In order to electrically
insulate such connections, a potting material 57 can be applied to
the outer side 23b of the printed circuit board 23. Preferably, as
seen in FIGS. 2 and 3, a potting dam 59 surrounds the section of
the printed circuit board 23 that is to be potted. For example, an
aluminum angle piece can have one flange 59f cut at the corners and
bent to form an enclosure. The cut flanges are secured to the
printed circuit board, such as, for example, by the mounting screws
37.
The potting dam 59 not only confines the potting material 57, but
can also serve as mounts for various types of components. For
instance, connectors such as the communications connector 61 can be
mechanically mounted in an opening 63 in the upright flange 65 of
the potting dam 59. External leads 49c connected to these
connectors 61 are then bent at a right angle to penetrate the PCB
23 through a connection 45 as described above.
Another example of a component which can be supported by the
potting dam 59 is the light emitting diode (LED) 67 which is
mounted in an opening 69 in the upright flange 65 of the potting
dam 59. Again, the external leads 471 for the LED are bent at right
angles and are connected to the printed circuit board 23 by a
connection 45.
Still another example of a component mounted on the printed circuit
board 23 forming the closure for the housing 19 is an auxiliary
current transformer (CT) 71. As shown in FIG. 3, such auxiliary CTs
71 come mounted on a platform 73 having four pins 49p(1), 49p(2),
and 49s(1) and 49s(2), which form electrical connections for the
primary and secondary windings of the CT as well as mechanically
supporting the CT 71 on the printed circuit board 23. The pins
49p(1) and 49p(2) for the primary winding of the CT formed by the
wire 49p are inserted into third plated through apertures 51p from
the outer side 23b of the printed circuit board 23 as shown in
FIGS. 4C and 5C. As the CT primary windings 49p are connected to
main CTs (not shown) external to the enclosure 17, the
corresponding leads 49q connected to the main CTs also penetrate
fourth apertures 53q from the outer side 23b of the PCB 23. The
corresponding apertures 51p and 51q are connected on the inner side
23a of the PCB 23 by the associated conductive traces 55p to
complete the connections 45'. Other components, typically mounted
on platforms, can be mounted to the printed circuit board 23 in a
similar manner either on the inner side 23a or the outer side
23b.
Another example of a component which can be mounted on the PCB 23
is a burden resistor 75 for converting the currents sensed by the
CTs into voltages for input to the relay. In this case, each
connection 45" for the ends of the burden resistor 75 include, as
shown in FIGS. 4B and 5B, three apertures: a first aperture 51a in
which the lead to the relay is soldered, a second aperture 51b to
which a pin 49s(1) for the secondary coil of the CT 71 is soldered
and an additional aperture 51r in which one lead 77 from the burden
resistor 75 is soldered by solder 53. These three apertures are
then connected by an associated common conductive trace 55s. A
similar connection is made to the other end of the burden resistor,
CT secondary winding and relay lead so that the burden resistor 75
is connected across the secondary winding of the auxiliary CT
71.
While specific embodiments of the invention have been described in
detail, it will be appreciated by those skilled in the art that
various modifications and alternatives to those details could be
developed in light of the overall teachings of the disclosure.
Accordingly, the particular arrangements disclosed are meant to be
illustrative only and not limiting as to the scope of invention
which is to be given the full breadth of the claims appended and
any and all equivalents thereof.
* * * * *